Insulating clothing is worn by both civilian and military personnel in many situations in which such personnel are exposed to cold and/or wet conditions. Suits and boots lined with insulating material might be used by land, air or naval personnel in any number of situations requiring warmth and/or protection from the elements, including water. As such individuals go about their tasks it is not unusual for them to perspire, perhaps heavily, and it becomes very desirable to remove such perspiration as quickly and completely as possible for the health and comfort of the individuals. This is particularly true when such individuals are working in the presence of water.
Insulation in the form of closed-cell foam materials maintains its insulating properties when immersed since water cannot penetrate into the cells of the foam material, which remain full of air. However, such materials do not permit the passage of perspiration from one side of the foam to the other. Alternatively, a composite can be made from vapour-permeable insulation such as battings, down and feathers, pile, or woven textile fabrics and then made essentially waterproof by being encased in an outer shell of a liquid-water impermeable, but water-vapour permeable fabric. Such a composite can fail if the seams of the encasing fabric fail or leak or if the encasing fabric deteriorates with age or contamination by oils, dirt, detergents or chemicals, etc. Once the outer shell leaks the insulating layer becomes wet and useless. Garments incorporating this type of composite also fail on immersion if water enters through closures at the neck, cuffs or ankles.